Fix CocoaPods (#3825)

### Goals :soccer:
Fix CocoaPods

### Implementation Details :construction:
Change podspec to adapt the file structure change.

Alamofire.podspec

@@ -15,7 +15,7 @@ Pod::Spec.new do |s|
 
   s.swift_versions = ['5']
 
-  s.source_files = 'Source/*.swift'
+  s.source_files = 'Source/**/*.swift'
 
   s.frameworks = 'CFNetwork'
 end